Liquid cooled resistor



United States Patent 3,108,243 LIQUID COOLED RESISTOR Berti] Lemar andRoger Myidebust, Ludvika, Sweden, assignors to Allmanna SvenskaElektriska Aktiebolaget, Vasteras, Sweden, a corporation of Sweden FiledSept. 18, 1961, Ser. No. 138,686 7 Claims. (Cl. 338-54) The presentinvention relates to a means for power resistance comprising resistorunits consisting of resistors placed inside tubes of electricallyinsulated material so that the said units are connected to a commonelectrical and mechanical connection point.

Within diiferent fields of elect-ro-technique, for example, high voltagedirect current, with certain damping processes, great amounts of energymust be destroyed in damping resistances. If these damping resistancesto all parts lie on a high potential, construction problems arise inbuilding the resistor and cooling since it is desirable to have a pumpaggregate and control equipment on the earth potential. It is alreadyknown to produce power resistances of the above mentioned type byplacing the resistance in an oil-filled vessel so that the end points ofthe resistances must be connected to high voltage bushing insulators. Itis also known to produce power resistances such as air-cooledresistances, but for higher powers these resistances are very bulky andexpensive. Even a power resistance according to the first mentioned typeis very expensive, partly because of the considerable oil quantity whichis required to fill the vessel and partly because of the relativelyexpensive high voltage bushing insulators. Further, the considerable oilquantity required for such a device is unsatisfactory from the fire riskpoint of view.

The device according to the invention offers a cheap construction whereinsulating elements in the construction serve as both supportingconstruction par-ts and as cooling channel systems, and Where the volumeof fluid required for cooling and insulating is reduced.

The invention is characterised in that said units at their commonconnection point are mounted on a tubeshaped pillar of insulatingmaterial provided to insulate the electrical connection point of theresistance units from the earth potential.

The invention will be described in the following with reference to theaccompanying schematical drawing in which FIGURE 1 shows a partly cutview of a construction according to the invention and FIGURE 2 the samedevice seen from above.

The device shown in FIGURE 1 comprises resistance units 1 which aremechanically and electrically connected to a metallic expansion vessel2, which also acts as control chamber for the cooling medium. Theexpansion vessel 2 is in its turn mounted on an insulating pillar 3which is provided with an insulating tube 4 concentrically placed in theinsulating pillar 3. The lower opening of the insulating tube 4 opensinto a tube 9 which is in connection with a pump aggregate 6. The pumpaggregate 6 is connected by means of a tube 7 on its pressure side, to acooler 8, which by means of a tube is connected to the lower opening ofthe ringshaped channel which is formed between the insulating tubes 3and 4. Each of the resistance units 1 consists of an outer insulatingtube 14 and an inner insulating tube 13. The space between saidinsulating tubes is partly fill-ed by a resistance winding 19 which atone end is connected to the output 11 and at the other end is connectedto the expansion vessel 2 and thus its connection point. The innerinsulating tube 13, as the resistance winding 19, is kept in itsposition inside the outer tube 14 by means of an insulating draw bolt12. Each resistance is 3,108,243 Patented Oct. 22, 1963 further providedwith a flash-over ring 15 and with exhaust pipes 16 which connect theupper part of the ringshaped cooling channel of each resistance unitwith the upper part of the expansion vessel. In the expansion vessel isalso arranged a float 18 which, via an insulating rod 19, is provided,by means of a member not shown, to give a signal or effect adisconnecting of the resistor if the oil level in the expansion vesselbecomes too low.

The resistance element 1 and expansion vessel 2 which have a highpotential are insulated from the earth potential with the help of thetubesshaped insulator pillar 3. When power is developed in theresistances 10 these must be cooled, otherwise they would be rapidlydestroyed. In the construction a fluid cooling medium is used, which bymeans of the pump 6 via the tube 7, cooler S and tube 9 is pumped outinto the ring-shaped channel which is formed between the insulatingtubes 3 and 4 and which terminates in a control chamber situated in thelower part of the expansion vessel 2. The outflow of the ringchannel isthrough the opening 20' in the control chamber connected to the innerinsulating tube 13 in one of the resistance elements 1A. The coolingmedium flows through the opening 20 and through the insulating tube 13,after which it is led into the ring-channel between the tubes 14 and 13.During its passage through the ring-channel, the cooling fluid flowspast the resistance 16 in the first resistance unit 1A so that the heatenergy developed in the resistance is led off. The cooling medium is ledfurther from the resistance unit 1A to the resistance unit 113 through atube 21 which opens into the inner tube 13 in the resistance unit 18.The cooling medium passes through the resistance unit 113 in the sameway as through 1A and is led further through the tube 22 to theresistance unit 1C, the outer ring-channel of which opens into theexpansion vessel 2. The cooling medium circulates further from theexpansion vessel 2 through the insulating tube 4 and conduit 5 via thepump 6 and tube 7 to the cooler 8 where the cooling medium is cooled. Inorder to prevent the formation of air pockets in the ring-channelbetween the tubes 13 and 14 in the resistance units, exhaust pipes 16are arranged between the upper part of the ring-channel between thetubes 13 and M and the upper part of the expansion vessel 2. In order toprotect the expansion vessel and the conduits attached to this fromflash-over across the resistances or between the common connection pointand earth a metallic flash-over ring 15 is airanged at the junctionbetween the resistance units and the expansion vessel 2. Since the airin the upper part of the expansion vessel should be as dry as possible,a container 17 containing a material which absorbs humidity is arrangedin the communication between the expansion vessel and open air. Tocontrol the oil level in the expansion vessel 2 a float 18 and aninsulating rod 19 joined to this are arranged to influence a controldevice so that a signal or disconnection of the resistance occurs whenthe oil level becomes too low.

The embodiments of the invention described herein have been foundparticularly advantageous for damping resistances subject to great andcontinual load. -It is, however, possible within the scope of theinvention, to carry out other constructive solutions to the problemwithout altering the principle of the method of operation of theinvention.

We claim:

1. Power resistance means comprising a plurality of units each includingan outer tube of electrically insulating material and a resistancemounted in said tube, a tube-shaped pillar of insulating material, saidouter tubes and said pillar having concentrically mounted inner tubestherein with their outer walls spaced from. the inner walls of the outertubes and the pillar, said outer tubes each having its inner endsupported by said pillar above the bottom thereof so as to. insulatethem from earth potential, said inner ends being electrically connected,and means interconnecting the interiors of the inner tubes and thespaces between the outer walls of the inner tubes and the inner walls ofthe outer tubes and pillar to form a passage through said interiors andspaces in series, said resistances being positioned in said passage soas to be contacted by a cooling medium flowing therethrough.

2. In a power resistance means as claimed in claim 1, saidinterconnecting means producing flow inone direction with respect to theinner ends of the tubes in all of the inner tubes within the outer tubesand flow in the opposite direction in all of the spaces between theouter and the inner tubes.

3. In a power resistance means as claimed in claim 1,

said resistances being mounted in the spaces between the outer tubes andthe inner tubes.

4. In an apparatus as claimed in claim 1, the outer free ends of theunits being lower than the inner ends.

5. In an apparatus as claimed in claim 1, means forming an expansionchamber extending upwardly from the column above the inner ends of theunits, said expansion vessel having internal Walls therein forming apart of said passage forming means.

6. In an apparatus as claimed in claim 5, exhaust pipes connecting theexpansion chamber with the upper part of each of the spaces between theinner tubes and the outer tubes.

7. In an apparatus as claimed in claim 5, float means in said expansionchamber responsive to the level of liquid therein to sense the level ofsuch liquid.

References Cited in the file of this patent UNITED STATES PATENTS1,101,050 Baerl ocher June 23, 1914 1,320,890 Moifat Nov. 4, 19191,365,421 MacKay Ian. 11, 1921 2,735,057 Schaelchlin Feb. 14, 1956

1. POWER RESISTANCE MEANS COMPRISING A PLURALITY OF UNITS EACH INCLUDINGAN OUTER TUBE OF ELECTRICALLY INSULATING MATERIAL AND A RESISTANCEMOUNTED IN SAID TUBE, A TUBE-SHAPED PILLAR OF INSULATING MATERIAL, SAIDOUTER TUBES AND SAID PILLAR HAVING CONCENTRICALLY MOUNTED INNER TUBESTHEREIN WITH THEIR OUTER WALLS SPACED FROM THE INNER WALLS OF THE OUTERTUBES AND THE PILLAR, SAID OUTER TUBES EACH HAVING ITS INNER ENDSUPPORTED BY SAID PILLAR ABOVE THE BOTTOM THEREOF SO AS TO INSULATE THEMFROM EARTH POTENTIAL, SAID INNER ENDS BEING ELECTRICALLY CONECTED, ANDMEANS INTERCONNECTING THE INTERIORS OF THE INNER TUBES AND THE SPACESBETWEEN THE OUTER WALLS OF THE INNER TUBES AND THE INNER WALLS OF THEOUTER TUBES AND PILLAR TO FORM A PASSAGE THROUGH SAID INTERIORS ANDSPACES IN SERIES, SAID RESISTANCES BEING POSITIONED IN SAID PASSAGE SOAS TO BE CONTACTED BY A COOLING MEDIUM FLOWING THERETHROUGH.